Eleanor, You could use a safety cone to build the piece on to make it hollow and remove after the cement mix starts to set up. You could also use tomato cages turned up side down with it's legs wired together, wrap cage with wire hardware cloth. Start by covering with a thin layer of cement mix. Then keep adding layers until you reach the desired size for carving.
I think some adults could have problems lifting any cement mix pieces. How about a cement mix base and a wood figure attached?
Just had a thought, wonder if you could make this like a garden totem. Have you seen the ones on this site? We usually make pieces using plastic bowls for molds, drill a hole through the center of the cement piece and pile them on top of each other on a piece of rebar or dowel that's driven into the ground. I'm thinking you could make pieces of cement mix and alternate wood blocks or wood balls (bocce balls or Croquet balls) or pvc tubing. Would you need the actual chess figure on top or could you letter the chess piece name on the top.
Hypertufa is waterproof and durable and can be painted/stained. The original recipe called for peat moss which wears away in the weather leaving a pockmarked surface. I can't think of the name of the place in New Zealand that use to make hypertufa. They were online...Timpy...don't remember but if you do a search I'm sure you'll find it. Keep us posted how you make out.
I'm pretty sure also that if you do a search on this forum you see the lanterns. Believe if you search this whole site you see the ones on the Japanese forum too. Billie

Some people make paper crete sculptures. Not sure exactly what it is but I think it may be lighter than hypertufa. The hypertufa forum would have info. What ever you do, I suggest that you use sand castle bucket molds for the rooks.
Heres one of mine in cement and painted black (been through one winter so far):

{{gwi:74214}}

Sounds like a very fun project. Please post the finished product. I'd love to see it.

kathy

I didn't realize I was in the hypertufa forum. Whoops.

kathy

How did you make an outdoor chess board? Could you post a picture?

Will take a picture tomorrow and have a go at posting it here. Basically, we laid coloured concrete pavers which we sealed with the addition of anti-slip grit. Then we swept a self-setting kind of mortar between the pavers which sets when watered- brilliant stuff.

I have been researching ingredients for papercrete. Our local waste exchange has free waste wool fleeces available. Anyone tried this in papercrete? Or polyester fibres for that matter -as in pillow stuffings? I see some discussion of these materials in making hypertufa and a suggestion that they help prevent cracking. How fine does the paper/etc have to be to work in papercrete?

Eleanor, Papercrete isn't waterproof. Check this forum to see if there is a way to waterproof it. Billie

Hi again

I got the impression from a posting on this forum that some waterproofing is achieved through sealing with polyurethane. Is that not your experience Bille?
Below is a link to a pic of the chess set.

Here is a link that might be useful: Chess set

Waterproofing is discussed in the link below. Would seem it might be ok if resealed occasionally.

Here is a link that might be useful: link to papercrete tutorial

there are lots of postings, pictures about lanterns. Some are wired, some for candles only. I make only Japanese style lanterns, very traditional and authentic look.

I found one lantern picture for you, switch to Gallery , go to page 2, there is one posting from packrat2 , very nice job.

Love the chess board. Wish I had room here. Hmm. Maybe the driveway, lol.
kathy

Kiwi, your chess idea is great, and papercrete would be much lighter to handle, and you can use recycables. if mixed with portland and sand it will hold up, but i would definately seal it.
i have made a few lanterns, i used mostly plastic pots and containers.i put a few pics.

Here is a link that might be useful: tufa lantern

Just fyi.I know you want to make your own pieces but check out this link. Don't think you could beat it for cost,weight,durability,or attractiveness. Not sure they'll ship to New Zealand though.My neighbor had a set but his dog kept urinating on them so he gave it to his daughter.

Here is a link that might be useful: garden chess